Noise modulation for on-chip noise measurement

ABSTRACT

Functionality for estimating characteristics of an on-chip noise signal can be implemented on a processing module. An on-chip noise signal is determined at an on-chip determination point of a computer chip. The on-chip noise signal is converted to a frequency-varying signal using a voltage-controlled oscillator implemented on the computer chip. The frequency-varying signal is measured at an off-chip measurement point and frequency information is extracted from the frequency-varying signal. The frequency information is converted to a voltage level associated with the on-chip noise signal based on the relationship between an input voltage provided to the voltage-controlled oscillator and an output frequency generated by the voltage-controlled oscillator.

RELATED APPLICATIONS

This application is a Continuation of, and claims the priority benefitof, U.S. application Ser. No. 14/299,257 filed Jun. 9, 2014, whichclaims the priority benefit of U.S. application Ser. No. 14/228,472filed Mar. 28, 2014.

BACKGROUND

Embodiments of the inventive subject matter generally relate to thefield of computing devices and, more particularly, to noise modulationfor on-chip noise measurement.

The performance of a computer chip may be affected by noise (e.g.,cross-talk with other signals, electromagnetic noise, interference,etc.). It is necessary to characterize the noise experienced on thecomputer chip (“on-chip noise”) to design the computer chip for noisetolerance, to cancel the noise at the computer chip, etc.

SUMMARY

Various embodiments for on-chip noise measurement are disclosed. In oneembodiment, an on-chip noise signal is determined at an on-chipdetermination point on a computer chip. The on-chip noise signal isconverted to a frequency-varying signal using a voltage-controlledoscillator. The frequency-varying signal is provided to an off-chipnoise estimation unit that is external to the computer chip. Frequencyinformation is extracted from the frequency-varying signal. Thefrequency information is converted to a voltage level associated withthe on-chip noise signal.

BRIEF DESCRIPTION OF THE DRAWINGS

The present embodiments may be better understood, and numerous objects,features, and advantages made apparent to those skilled in the art byreferencing the accompanying drawings.

FIG. 1 is a block diagram illustrating example operations for on-chipnoise estimation.

FIG. 2 is an example conceptual diagram illustrating post-processing ofa frequency-varying signal to determine characteristics of the on-chipnoise signal.

FIG. 3 is a flow diagram illustrating example operations for on-chipnoise estimation.

FIG. 4 is a flow diagram illustrating example operations for processinga frequency-varying output signal to estimate characteristics of anon-chip noise signal.

FIG. 5 is a flow diagram illustrating example operations for mapping aninput voltage level provided to a voltage-controlled oscillator (VCO) toan output frequency generated by the VCO.

FIG. 6 is a block diagram illustrating one embodiment of an electronicdevice including a mechanism for on-chip noise estimation.

DESCRIPTION OF EMBODIMENT(S)

The description that follows includes exemplary systems, methods,techniques, instruction sequences, and computer program products thatembody techniques of the present inventive subject matter. However, itis understood that the described embodiments may be practiced withoutthese specific details. For instance, although examples refer toestimating noise characteristics on a computer chip, embodiments are notso limited. In other embodiments, functionality for estimating the noisecharacteristics can be implemented for a group of computer chips.Furthermore, although examples refer to estimating characteristics of anoise signal; in other embodiments, the operations described herein maybe executed to estimate the characteristics of other types of signals(e.g., data signals). In other instances, well-known instructioninstances, protocols, structures, and techniques have not been shown indetail in order not to obfuscate the description.

Noise estimation and compensation relies on knowledge of thecharacteristics of the noise signal (e.g., amplitude, periodicity, etc.)within a computer chip (“on-chip noise signal”) implemented on aprocessing module. However, because of limited access to the computerchip, it may not be possible to measure the on-chip noise signal at anon-chip determination point. Existing techniques employ connectingtraces or wires between the on-chip noise determination point and aremote measurement point (or “off-chip measurement point”) at theexterior of the processing module to measure the on-chip noise signal.However, signal degradation sources (e.g., connecting traces and wires,processing module housing, interference/cross-talk from other signals,etc.) can degrade the noise signal as the noise signal travels from theon-chip determination point to the off-chip measurement point. Thissignal degradation can affect the characteristics of the on-chip noisesignal (e.g., amplitude, shape, and nature of the on-chip noise signal).Consequently, the on-chip noise signal received at the off-chipmeasurement point may have different characteristics from and may be aninaccurate measure of the on-chip noise signal.

A voltage-controlled oscillator (VCO) can be implemented within thecomputer chip to estimate characteristics of the on-chip noise inreal-time (or approximately real-time) without disrupting normal systemoperation. The on-chip noise signal is sampled and provided as an inputto the VCO. The VCO generates a frequency-varying sinusoidal signal withinstantaneous frequencies that correspond to the voltage levels of theon-chip noise signal. The frequency-varying signal is provided through atransfer channel (e.g., a connecting trace) to an off-chip measurementpoint (e.g., a measurement pin/node at the exterior of a processingmodule that includes the computer chip). Although the amplitude of thefrequency-varying signal is prone to signal degradation described above,the frequency content of the frequency-varying signal suffers negligibledegradation. The frequency-varying signal can be further processed todetermine voltage level variations of the on-chip noise signal.Representing the voltage level of the on-chip noise signal by frequencyvariations of a sinusoidal signal can minimize the effects of signaldegradation. This can ensure that the characteristics of the on-chipnoise signal that are measured at the off-chip measurement point are anaccurate representation of the actual characteristics of the on-chipnoise signal. Accurate estimation of the on-chip noise signal may alsohelp in designing the computer chip for noise tolerance and/or noisecancellation, in real-time noise cancellation, and in achieving optimalperformance.

FIG. 1 is a block diagram illustrating example operations for on-chipnoise estimation. FIG. 1 depicts a processing module 102 and an off-chipnoise estimation unit 110. The processing module 102 includes at leastone computer chip 104. The computer chip 104 includes an on-chip noisedetermination unit 106 and a voltage-controlled oscillator (VCO) 108.The processing module 102 may be a printed circuit board (PCB) oranother suitable module that includes one or more computer chips. Thecomputer chip 104 may be a processor chip, a memory chip, an integratedcircuit (IC), a system-on-a-chip (SoC), an application-specific IC(ASIC), etc. The off-chip noise estimation unit 110 comprises awindowing unit 112, a Fourier Transform unit 114, and a noiseinformation estimator 116.

As described above, it may not be possible to measure the on-chip noisesignal 118 at an on-chip determination point. Instead, the measurementpoint 124 for measuring the on-chip noise signal 118 may be external tothe computer chip 104, as depicted in FIG. 1. The voltage level (alsoreferred to as amplitude or waveform shape) of a signal may be highlyprone to interference and loss through the processing module 102.However, the frequency of the signal may be less prone to interferenceand loss. The VCO 108 can help combat the effects of interference andloss at an off-chip measurement point 124. The on-chip noisedetermination unit 106 may periodically sample the on-chip noise signal118 and provide the sampled noise signal as a control signal to the VCO108. The control signal (i.e., a sample of the on-chip noise signal 118)controls the instantaneous oscillation frequency of a frequency-varyingsinusoidal signal 120 generated by the VCO 108. For example, a 10 mVcontrol signal may cause VCO 108 to generate a 10 MHz output signal; a20 mV control signal may cause the VCO 108 to generate a 20 MHz outputsignal; and so on. The frequency-varying signal 120 is provided from theVCO 108 to the off-chip noise estimation unit 110 via systeminterconnect wiring 109. The system interconnect wiring 109 mayrepresent physical connections (e.g., wires, traces, vias, etc.) betweenthe computer chip 104 and the off-chip noise estimation unit 110. Thesystem interconnect wiring 109 may affect the voltage level of thefrequency-varying signal 120 and cause distortion and amplitudevariations in the frequency-varying signal 120. Signal 121 representsthe frequency-varying signal that is received by the off-chip noiseestimation unit 110. The peak-to-peak amplitude of the frequency-varyingsignal 121 at the input of the noise estimation unit 110 may or may notremain the same as that of the frequency-varying signal 120 generated bythe VCO 108. However, the instantaneous frequency of thefrequency-varying signal 121 may be the same or approximately the sameas the corresponding instantaneous frequency of the frequency-varyingsignal 120. Thus, the amplitude variations of the on-chip noise signal118 may be carried over by frequency modulation of a sinusoidal signalassociated with the VCO 108.

The frequency-varying signal 121 is provided to the noise estimationunit 110 via the off-chip measurement point 124 (e.g., a processingmodule pin, a PCB probe node, etc.). The noise estimation unit 110 mayfurther process and extract frequency information from thefrequency-varying signal 121. For example, the windowing unit 112 mayexecute time-windowing operations by dividing the frequency-varyingsignal 121 into multiple consecutive time intervals (“windows”). Foreach time interval, the Fourier transform unit 114 may execute Fouriertransform operations on samples within the time interval to convert thesamples from the time-domain to the frequency-domain. For each timeinterval, executing the Fourier transform operations can yield frequencyinformation associated with the portion of the frequency-varying signal121 that lies within the time interval, as will be further describedwith reference to FIG. 2.

FIG. 2 is an example conceptual diagram illustrating post-processing ofthe frequency-varying signal to determine characteristics of the on-chipnoise signal. The off-chip noise estimation unit 110 receives thefrequency-varying signal 121 generated by the VCO 108 and measured atthe off-chip measurement point 124. The windowing unit 112 applies asuitable windowing function to the frequency-varying signal 121 to yielda portion (or window represented by W in FIG. 2) of thefrequency-varying signal 121 for subsequent analysis. As depicted inFIG. 2, the windowing unit 110 applies the windowing function togenerate a first sub-signal 202 from the frequency-varying signal 121 ata first time instant (t=0). The first sub-signal 202 is then provided tothe Fourier transform unit 114. The Fourier transform unit 114 canexecute Fourier transform operations (e.g., Fast Fourier Transform (FFT)operations) on the first sub-signal 202 to yield a correspondingfrequency-domain signal 210. The frequency-domain signal 210 comprisesresonant peaks at corresponding resonant frequencies 218 and 220A. Insome embodiments, the resonant peak and the corresponding resonantfrequency may be identified by comparing the amplitude of thefrequency-domain signal 210 against a predefined threshold. Thefrequencies at which the amplitude of the frequency-domain signal 210exceeds the predefined threshold may be designated as resonantfrequencies. As described above, the VCO 108 converts an input voltagelevel into an output frequency. Therefore, the resonant frequencies 218and 220A correspond to a first voltage level and a second voltage levelof the on-chip noise signal 118, respectively.

Furthermore, as depicted in FIG. 2, the windowing unit 112 applies thewindowing function to generate a second sub-signal 204 at a second timeinstant (t=1), a third sub-signal 206 at a third time instant (t=2), afourth sub-signal 208 at a fourth time instant (t=3), and so on. Thetime instants t=0, 1, 2, 3, etc. may refer to the time instants at whichthe windowing function is applied to the frequency-varying signal 121.The Fourier transform unit 114 can successively execute Fouriertransform operations on the sub-signals 204, 206, and 208 to yieldfrequency-domain signals 212, 214, and 216 respectively. Thefrequency-domain signal 212 comprises resonant peaks at resonantfrequencies 220B and 222; the frequency-domain signal 214 comprises aresonant peak at resonant frequency 224A; and the frequency-domainsignal 216 comprises resonant peaks at resonant frequencies 224B and226. As discussed above, the resonant peak and the correspondingresonant frequency may be identified by comparing the amplitude of eachfrequency-domain signal 212, 214, and 216 against a predefinedthreshold. The frequencies at which the amplitude of thefrequency-domain signals 212, 214, and 216 exceed the predefinedthreshold may be designated as resonant frequencies.

Referring back to FIG. 1, after identifying the resonant frequencies,the noise information estimator 116 (e.g., a frequency-to-voltagetranslation unit) can map the resonant frequencies to a correspondingvoltage level of the on-chip noise signal 118 using avoltage-to-frequency conversion structure. The voltage-to-frequencyconversion structure may represent the relationship between the inputvoltage level provided to the VCO 108 (i.e., the on-chip noise signal118) and output frequency generated by the VCO 108 (i.e., theinstantaneous frequency of the frequency-varying signal 120). The noiseinformation estimator 116 can also execute a calibration process(further described in FIG. 5) to determine the voltage-to-frequencyconversion structure (e.g., a graph, a table, or another suitable datastructure). The calibration operations may be executed periodically, onstart-up, or in accordance with another suitable schedule. In oneembodiment, multiple reference DC voltage levels may be provided to theVCO 108 (instead of the on-chip noise signal 118). For each reference DCvoltage level, the VCO 108 may generate a sinusoidal output signal withan output frequency that corresponds to the reference DC voltage. Foreach reference DC voltage level, the frequency of the sinusoidal outputsignal may be measured at the exterior measurement point 124. Thevoltage-to-frequency conversion structure may be generated based onknowledge of the reference DC voltage levels and the correspondingoutput frequency. The calibration process can also account for process,voltage, and temperature variations and other uncertainties within thecomputer chip 104 that may affect the operation of the VCO 108.

The noise information estimator 116 can use the voltage-to-frequencyconversion structure to translate resonant frequencies determined fromthe frequency-domain signals 210, 212, 214, and 216 to correspondingvoltage levels of the on-chip noise signal 118. For example, theresonant frequencies 218 and 220A for the first sub-signal 202 (firstwindow) may correspond to a first and a second voltage level,respectively. The resonant frequencies 220B and 222 for the secondsub-signal 204 (second window) may correspond to the second voltagelevel and a third voltage level, respectively, and so on. In someembodiments, the noise information estimator 116 can determinevariations in the voltage level of the on-chip noise signal within atime interval (i.e., window). In another embodiment, the noiseinformation estimator 116 can determine variations in the voltage levelof the on-chip noise signal across consecutive time intervals. Inanother embodiment, the noise information estimator 116 can determinethe periodicity of the on-chip noise signal by identifying timeintervals that have the same frequency spectrum and/or the same resonantfrequencies. In another embodiment, the on-chip noise signal can bereconstructed based on knowledge of the voltage levels during each ofthe time intervals (as depicted by signal 122). The noise informationestimator 116 may track the presence, absence, and changes in theposition of the resonant frequencies across the Fourier transforms ofthe different time intervals to determine the sequence of the resonantfrequencies. Based on the sequence of the resonant frequencies, thenoise information estimation unit 116 may determine the variation involtage level of the on-chip noise signal with time.

It is noted that in some embodiments, the time intervals (windows) forexecuting the Fourier transform operations may be selected so thatconsecutive time intervals overlap with each other and so that thesampling period is much smaller than the width of the time interval. Afairly accurate reconstruction of the on-chip noise signal may beachieved by selecting overlapping time intervals. Additionally, in someembodiments, the time intervals for executing the Fourier transformoperations may be narrow so that there is one resonant frequency pertime interval, thus improving the accuracy of the reconstructed on-chipnoise signal.

FIG. 3 is a flow diagram (“flow”) 300 illustrating example operationsfor on-chip noise estimation. The flow 300 begins at block 302.

An on-chip noise signal is sampled at an on-chip determination point(block 302). For example, the on-chip noise determination unit 106 maysample the on-chip noise signal 118 measured at an on-chip determinationpoint. The flow continues at block 304.

The noise signal is provided as an input to an on-chip voltagecontrolled oscillator (block 304). As discussed above with reference toFIGS. 1 and 2, the noise signal controls the oscillation frequency ofthe VCO 108. A VCO can generate a frequency-varying signal with aninstantaneous frequency that is proportional to an instantaneous voltagelevel of an on-chip noise signal. Because the voltage level of anon-chip noise signal varies with time, the instantaneous frequency ofthe frequency-varying signal also varies with time. In some embodiments,the fundamental oscillation frequency (or natural oscillation frequency)of a VCO may correspond to a zero input signal (e.g., a 1 V on-chipnoise signal). As the voltage level of the on-chip noise signal variesin the positive (or negative) direction, the oscillation frequency ofthe VCO may also increase (or decrease) relative to the fundamentaloscillation frequency. The accuracy of the on-chip noise measurement maydepend on the processing speed of the VCO. The flow continues at block306.

The frequency-varying signal generated by the voltage controlledoscillator is measured at an off-chip measurement point (block 306). Thefrequency-varying signal may be transmitted from the output of anon-chip VCO to the off-chip measurement point via a transfer channel(e.g., a PCB trace, a physical wire, etc.). Converting voltage levelvariations of the on-chip noise signal into corresponding frequencyvariations of the frequency-varying signal can help minimize signaldegradation caused by the transfer channel. The flow continues at block308.

The frequency-varying signal is processed to estimate characteristics ofthe on-chip noise signal (block 308). For example, an off-chip noiseestimation unit can process the signal to determine the characteristicsof the on-chip noise signal (e.g., variation of voltage level with time,periodicity, etc.). Operations for estimating the characteristics of theon-chip noise signal from the frequency-varying signal are furtherdescribed in FIGS. 1-2 and 4. From block 308, the flow ends.

FIG. 4 is a flow diagram 400 illustrating example operations forprocessing a frequency-varying output signal to estimate characteristicsof an on-chip noise signal. The flow 400 begins at block 402.

A frequency-varying signal generated by a voltage-controlled oscillatoris received in response to an on-chip noise signal (block 402). Asdescribed above, an on-chip noise signal is provided as an input to anon-chip VCO. The VCO can generate the frequency-varying signal with aninstantaneous frequency that is proportional to the instantaneousvoltage level of the on-chip noise signal. The flow continues at block404.

Windowing operations are executed on the frequency-varying signal (block404). For example, a windowing function can be applied to thefrequency-varying signal to select a portion (window) of thefrequency-varying signal for subsequent spectral analysis. In someembodiments, a rectangular windowing function may be applied to thefrequency-varying signal. In other embodiments, another suitablewindowing function may be applied to the frequency-varying signal. Insome embodiments, the frequency-varying signal may be sampled and thewindowing operations may be executed on samples of the frequency-varyingsignal. In some embodiments, the windows for executing the Fouriertransform operations may be selected so that consecutive time intervalsoverlap with each other and so that the sampling period between windowsis much smaller than the duration of the window. This can help achieve afairly accurate reconstruction of the on-chip noise signal.Additionally, in some embodiments, the windows for executing the Fouriertransform operations may be narrow so that there is one resonantfrequency per time interval, thus improving the accuracy of thereconstructed on-chip noise signal. The VCO is typically configured togenerate a range of frequencies between a lower frequency limit (f₁) andan upper frequency limit (f₂). The windowing function and the durationof the window (window size) may be selected based, at least in part, onthe lower frequency limit of the VCO. For example, the duration of thewindow may be at least one time period of the lower frequency limit(e.g., 1/f₁). The flow continues at block 406.

Fourier transform operations are executed on the windowedfrequency-varying signal to determine frequency information associatedwith the on-chip noise signal (block 406). As described with referenceto FIG. 2, the Fourier transform operations can be executed for eachwindow of the time-domain frequency-varying signal to yield acorresponding frequency-domain signal. In some embodiments, theamplitude of the frequency-domain signal may be compared against apredefined threshold. The amplitudes that exceed the predefinedthreshold may be referred to as “resonant peaks” the frequency-domainsignal and the frequencies that correspond to the resonant peaks may bereferred to as resonant frequencies. The resonant frequencies and thecorresponding window of the frequency-varying signal may be referred toas “frequency information” associated with the on-chip noise signal. Thefrequency information can be used to characterize the on-chip noisesignal, for example, as described in FIGS. 1-2. The flow continues atblock 408.

The frequency information associated with the on-chip noise signal istranslated to voltage levels associated with the on-chip noise signal(block 408). As described in FIGS. 1 and 5, VCO calibration operationsmay be executed to determine a voltage-to-frequency conversion structurethat represents the correlation between an input voltage level providedto a VCO and an output frequency generated by the VCO. Based on thevoltage-to-frequency conversion structure, each resonant frequency(determined at block 406) can be translated to a corresponding voltagelevel of the on-chip noise signal. Additionally, the voltage levels andthe corresponding window (i.e., time interval) can be used to estimatecharacteristics of the on-chip noise signal. For example, variations inthe voltage level of the on-chip noise signal may be determined within atime interval (i.e., window). As another example, variations in thevoltage level of the on-chip noise signal may be determined acrossconsecutive time intervals. In another embodiment, the periodicity ofthe on-chip noise signal may be determined by identifying time intervalsthat have the same frequency spectrum and/or the same resonantfrequencies. In another embodiment, the on-chip noise signal may bereconstructed based on knowledge of the voltage levels during each ofthe time intervals (as depicted by signal 122).

Characteristics of an on-chip noise signal can be used in conjunctionwith applications executing on a computer chip to determine whether toexecute noise cancellation operations. For example, the noisecancellation operations may not be executed if the maximum voltage levelof the on-chip noise signal lies below an acceptable noise level for theapplication(s) executing on the computer chip. In some embodiments, thecharacteristics of the on-chip noise signal can be fed back to a noisecancellation unit to fine-tune components of the noise cancellationunit. For example, the characteristics of the on-chip noise signal maybe used to estimate and tune coefficients of a filter unit. In someembodiments, the noise cancellation unit may be implemented on thecomputer chip 104. However, in other embodiments, the noise cancellationunit may not be implemented on the computer chip 104 or the processingmodule 102. In some embodiments, the characteristics of the on-chipnoise signal may be stored or provided to post processing units forsubsequent noise cancellation. From block 408, the flow ends.

FIG. 5 is a flow diagram 500 illustrating example operations for mappingan input voltage level provided to a VCO to an output frequencygenerated by the VCO. The flow 500 begins at block 502.

A plurality of reference direct current (DC) voltage levels are providedas an input to a VCO (block 502). As described above, the input voltagelevel that is provided to the VCO controls the frequency of a sinusoidalsignal generated by the VCO. To calibrate the VCO and to determine thecorrelation between the input voltage level and output frequency,multiple reference DC voltage levels (e.g., signals at 0 Hz withconstant amplitude) may be provided to the VCO. The number of referenceDC voltage levels provided to the VCO may depend on the characteristicsof the VCO. For example, if the VCO is a linear device, two reference DCvoltage levels may be sufficient to determine the correlation betweenthe input voltage level and output frequency. The flow continues atblock 504.

For each reference DC voltage level, the frequency of an output signalgenerated by the VCO is determined (block 504). The output signal may bea sinusoidal signal with a frequency that directly corresponds to thereference DC voltage level. Alternatively, the output signal may be atriangular signal, a square-wave signal, or a signal with anothersuitable waveform shape. Because the DC voltage level provided to theVCO has a constant amplitude, the output signal generated by the VCO hasa constant frequency. The frequency of the output signal may be measuredat an off-chip measurement point 124 (e.g., a measurement node at theexterior of a processing module, a PCB probe point, etc.). The flowcontinues at block 506.

A voltage-to-frequency conversion structure is generated based on theplurality of reference DC voltage levels and the corresponding frequencyof the output signal (block 506). A suitable interpolation and/orextrapolation technique may be executed to convert the discrete pairs ofreference DC voltage level and corresponding output frequency to avoltage-to-frequency conversion structure. For example, curve fittingoperations, regression operations, etc. may be employed to construct thevoltage-to-frequency conversion structure. The flow continues at block508.

The voltage-to-frequency conversion structure is used to translatefrequency information associated with an on-chip noise signal tocorresponding voltage levels associated with the on-chip noise signal(block 508). As described with reference to FIGS. 1-2 and 4, resonantfrequencies may be determined from a frequency-domain representation ofeach window of a frequency-varying output signal generated by the VCO.The resonant frequencies may be translated into corresponding voltagelevels based on the voltage-to-frequency conversion structure. Fromblock 508, the flow ends.

It should be understood that FIGS. 1-5 and the operations describedherein are examples meant to aid in understanding embodiments and shouldnot be used to limit embodiments or limit scope of the claims.Embodiments may perform additional operations, fewer operations,operations in a different order, operations in parallel, and someoperations differently. Although examples describe the noise estimationunit being implemented external to the computer chip and the processingmodule, embodiments are not so limited. In other embodiments, the noiseestimation unit may be implemented external to the computer chip but onthe processing module. In another embodiment, the noise estimation unitmay be implemented on the computer chip away from the on-chipdetermination point.

In some embodiments, the noise estimation operations described above maybe executed in real-time or quasi real-time (e.g., because of the timedelays associated with generating a window of the frequency-varyingsignal). However, in other embodiments, the noise estimation operationsmay be executed on previously stored noise signals or noise samples. Forexample, the on-chip noise signal may be sampled and stored. At a latertime, the stored noise samples may be provided to an on-chip VCO and thefrequency-varying signal generated by the VCO may be analyzed toestimate characteristics of the on-chip noise signal. As anotherexample, the on-chip noise signal may be sampled and provided to theVCO. The frequency-varying signal generated by the VCO may be stored. Ata later time, the stored frequency-varying signal may be analyzed (e.g.,sampled, windowed, Fourier transformed, etc.) to estimate thecharacteristics of the on-chip noise signal. In some embodiments, thenoise estimation operations may be executed while other applications areexecuting on the computer chip. In other embodiments, the noiseestimation operations may be executed at start-up or after disabling theapplications executing on a computer chip.

In some embodiments, the operations described above may be used toestimate application-specific noise characteristics. For example, afirst set of noise characteristics associated with executing aspreadsheet application and a second set of noise characteristicsassociated with executing a gaming application may be determined. Insome embodiments, the noise characteristics may vary depending on theapplication being executed because of differences in processor workload,switching activity, current demand, etc. The first and second sets ofnoise characteristics may be analyzed to determine whether and what typeof noise cancellation operations should be executed for the application.

Although examples refer to estimating characteristics of a noise signalmeasured on a computer chip, embodiments are not so limited. In otherembodiments, the operations for estimating the characteristics of anoise signal may be executed at a processing module level, for a groupof computer chips, etc. Operations for estimating the noisecharacteristics may be executed to estimate characteristics of anysuitable type of noise (e.g., power noise, high-frequency signal noise,etc.) and may be executed in a variety of environments (e.g., noisyenvironments, hazardous environments, remote measurement environments,etc.). For example, the operations described above may be used for noiseestimation on circuits (e.g., computer chips, integrated circuits, etc.)that have a limited number of input/output ports. As another example,when wirelessly measuring radiation that is dangerous to humans,radiation measurements may include noise from the environment. In thisexample, the operations described above may be executed to characterizethe noise (at the measurement point within the radiation environment)for subsequently designing/tuning filters to minimize the noise in theradiation measurement.

Finally, although FIG. 1 describes the noise estimation unit processingthe frequency-varying signal received from one VCO (and one computerchip), embodiments are not so limited. In other embodiments, the noiseestimation unit may process the frequency-varying signal received frommultiple VCOs. For example, a processing system may include multiplecomputer chips—each computer chip comprising an on-chip VCO. Thefrequency-varying signal generated by each of the on-chip VCOs may beprovided to a common off-chip noise estimation unit. The noiseestimation unit may execute operations described above to characterizethe on-chip noise signal associated with each of the computer chips. Inanother embodiment, the computer chip may include multiple determinationpoints (or measurement points) that are each associated with acorresponding on-chip VCO. In one example, a common off-chip noiseestimation unit may receive and process the frequency-varying signalgenerated by each VCO to characterize the on-chip noise signaldetermined at each determination point on the computer chip. However, inanother example, a common on-chip noise estimation unit may process thefrequency-varying signal to characterize the on-chip noise signaldetermined at each determination point if the on-chip noise estimationunit is not affected by noise.

As will be appreciated by one skilled in the art, aspects of the presentinventive subject matter may be embodied as a system, method, and/orcomputer program product. Accordingly, aspects of the present inventivesubject matter may take the form of an entirely hardware embodiment, anentirely software embodiment (including firmware, resident software,micro-code, etc.) or an embodiment combining software and hardwareaspects that may all generally be referred to herein as a “circuit,”“module” or “system.” Furthermore, aspects of the present inventivesubject matter may take the form of a computer program product embodiedin a computer readable storage medium (or media) having computerreadable program instructions embodied thereon. Furthermore, aspects ofthe present inventive subject matter may be a system, a method, and/or acomputer program product. The computer program product may include acomputer readable storage medium (or media) having computer readableprogram instructions thereon for causing a processor to carry outaspects of the present inventive subject matter.

The computer readable storage medium can be a tangible device that canretain and store instructions for use by an instruction executiondevice. The computer readable storage medium may be, for example, but isnot limited to, an electronic storage device, a magnetic storage device,an optical storage device, an electromagnetic storage device, asemiconductor storage device, or any suitable combination of theforegoing. A non-exhaustive list of more specific examples of thecomputer readable storage medium includes the following: a portablecomputer diskette, a hard disk, a random access memory (RAM), aread-only memory (ROM), an erasable programmable read-only memory (EPROMor Flash memory), a static random access memory (SRAM), a portablecompact disc read-only memory (CD-ROM), a digital versatile disk (DVD),a memory stick, a floppy disk, a mechanically encoded device such aspunch-cards or raised structures in a groove having instructionsrecorded thereon, and any suitable combination of the foregoing. Acomputer readable storage medium, as used herein, is not to be construedas being transitory signals per se, such as radio waves or other freelypropagating electromagnetic waves, electromagnetic waves propagatingthrough a waveguide or other transmission media (e.g., light pulsespassing through a fiber-optic cable), or electrical signals transmittedthrough a wire.

Computer readable program instructions described herein can bedownloaded to respective computing/processing devices from a computerreadable storage medium or to an external computer or external storagedevice via a network, for example, the Internet, a local area network, awide area network and/or a wireless network. The network may comprisecopper transmission cables, optical transmission fibers, wirelesstransmission, routers, firewalls, switches, gateway computers, and/oredge servers. A network adapter card or network interface in eachcomputing/processing device receives computer readable programinstructions from the network and forwards the computer readable programinstructions for storage in a computer readable storage medium withinthe respective computing/processing device.

Computer readable program instructions for carrying out operations ofthe present inventive subject matter may be assembler instructions,instruction-set-architecture (ISA) instructions, machine instructions,machine dependent instructions, microcode, firmware instructions,state-setting data, or either source code or object code written in anycombination of one or more programming languages, including an objectoriented programming language such as Smalltalk, C++ or the like, andconventional procedural programming languages, such as the “C”programming language or similar programming languages. The computerreadable program instructions may execute entirely on the user'scomputer, partly on the user's computer, as a stand-alone softwarepackage, partly on the user's computer and partly on a remote computeror entirely on the remote computer or server. In the latter scenario,the remote computer may be connected to the user's computer through anytype of network, including a local area network (LAN) or a wide areanetwork (WAN), or the connection may be made to an external computer(for example, through the Internet using an Internet Service Provider).In some embodiments, electronic circuitry including, for example,programmable logic circuitry, field-programmable gate arrays (FPGA), orprogrammable logic arrays (PLA) may execute the computer readableprogram instructions by utilizing state information of the computerreadable program instructions to personalize the electronic circuitry,in order to perform aspects of the present inventive subject matter.

Aspects of the present inventive subject matter are described hereinwith reference to flowchart illustrations and/or block diagrams ofmethods, apparatus (systems), and computer program products according toembodiments of the inventive subject matter. It will be understood thateach block of the flowchart illustrations and/or block diagrams, andcombinations of blocks in the flowchart illustrations and/or blockdiagrams, can be implemented by computer readable program instructions.

These computer readable program instructions may be provided to aprocessor of a general purpose computer, special purpose computer, orother programmable data processing apparatus to produce a machine, suchthat the instructions, which execute via the processor of the computeror other programmable data processing apparatus, create means forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks.

These computer readable program instructions may also be stored in acomputer readable storage medium that can direct a computer, aprogrammable data processing apparatus, and/or other devices to functionin a particular manner, such that the computer readable storage mediumhaving instructions stored therein comprises an article of manufactureincluding instructions which implement aspects of the function/actspecified in the flowchart and/or block diagram block or blocks.

The computer readable program instructions may also be loaded onto acomputer, other programmable data processing apparatus, or other deviceto cause a series of operational steps to be performed on the computer,other programmable apparatus or other device to produce a computerimplemented process, such that the instructions which execute on thecomputer, other programmable apparatus, or other device implement thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods, and computer program products according to variousembodiments of the present inventive subject matter. In this regard,each block in the flowchart or block diagrams may represent a module,segment, or portion of instructions, which comprises one or moreexecutable instructions for implementing the specified logicalfunction(s). In some alternative implementations, the functions noted inthe block may occur out of the order noted in the figures. For example,two blocks shown in succession may, in fact, be executed substantiallyconcurrently, or the blocks may sometimes be executed in the reverseorder, depending upon the functionality involved. It will also be notedthat each block of the block diagrams and/or flowchart illustration, andcombinations of blocks in the block diagrams and/or flowchartillustration, can be implemented by special purpose hardware-basedsystems that perform the specified functions or acts or carry outcombinations of special purpose hardware and computer instructions.

FIG. 6 is a block diagram of one embodiment of an electronic device 600including a mechanism for on-chip noise estimation. In some embodiments,the electronic device 600 can be a laptop computer, a tablet computer, anetbook, a mobile phone, a smart appliance, a wearable device, a gamingconsole, a desktop computer, a network bridge device, or other suitableelectronic device including processing capabilities. For example, theelectronic device 600 can be a network device that implementscommunication protocols for exchanging communications with anothernetwork device. The electronic device 600 includes a processor unit 602(possibly including multiple processors, multiple cores, multiple nodes,and/or implementing multi-threading, etc.). The electronic device 600includes a memory unit 606. The memory unit 606 may be system memory(e.g., one or more of cache, SRAM, DRAM, zero capacitor RAM, TwinTransistor RAM, eDRAM, EDO RAM, DDR RAM, EEPROM, NRAM, RRAM, SONOS,PRAM, etc.) or any one or more of the above already described possiblerealizations of computer-readable storage media. The electronic device600 also includes a bus 610 (e.g., PCI, ISA, PCI-Express,HyperTransport®, InfiniBand®, NuBus, AHB, AXI, etc.) and networkinterfaces 604. The processor unit 602, the memory unit 606, and thenetwork interfaces 604 are coupled to the bus 610. The networkinterfaces 604 include a wireless network interface (e.g., a WLANinterface, a Bluetooth® interface, a WiMAX interface, a ZigBee®interface, a Wireless USB interface, etc.) and/or a wired networkinterface (e.g., a powerline communication interface, an Ethernetinterface, etc.).

The electronic device 600 also includes an on-chip noise estimation unit608 coupled with a computer chip 612. The computer chip 612 includes anon-chip noise determination unit 616 and a VCO 614. The off-chip noiseestimation unit 608 includes a windowing unit 618, a Fourier transformunit 620, and a noise information estimator 622. The computer chip 612may be a memory chip, a processor chip, an integrated circuit (IC), anapplication-specific IC (ASIC), a system-on-a-chip (SoC), etc. In someembodiments, the computer chip 612 may be implemented within theprocessor unit 602, the memory unit 606, or another suitable processingunit. In another embodiment, the computer chip 612 may be the memoryunit 606 or the processor unit 602. For example, the processor unit 602may include an on-chip noise determination unit and a VCO. An off-chipnoise estimation unit may analyze the frequency-varying signal generatedby the VCO to characterize the on-chip noise signal of the processorunit 602. As discussed above with reference to FIGS. 1-5, the on-chipnoise determination unit 616 can sample the on-chip noise signal andprovide the noise samples to the VCO 614. The VCO 614 can convert theon-chip noise signal to a frequency-varying signal with an instantaneousfrequency that is proportional to the instantaneous voltage level of theon-chip noise signal. The windowing unit 618 can receive thefrequency-varying signal at an off-chip measurement point and executewindowing operations to yield a portion of the frequency-varying signal.The Fourier transform unit 620 can convert the portion of thefrequency-varying signal to a frequency-domain signal; while the noiseinformation estimator 622 can estimate characteristics of the on-chipnoise signal from the frequency-domain signal.

Any one of these functionalities may be partially (or entirely)implemented in hardware and/or on the processor unit 602. For example,the functionality of the noise estimation unit 608 may be implementedwith an ASIC, in logic implemented in the processor unit 602, in aco-processor on a peripheral device or card, etc. In some embodiments,the noise estimation unit 608 can be implemented on an SoC, an ASIC, oranother suitable integrated circuit that is distinct from the computerchip 612. Further, realizations may include fewer or additionalcomponents not illustrated in FIG. 6 (e.g., video cards, audio cards,additional network interfaces, peripheral devices, etc.). For example,in addition to the processor unit 602 coupled with the bus 610, thenoise estimation unit 608 may include at least one additional processorunit. As another example, although illustrated as being coupled to thebus 610, the memory unit 606 may be coupled to the processor unit 602.

While the embodiments are described with reference to variousimplementations and exploitations, it will be understood that theseembodiments are illustrative and that the scope of the inventive subjectmatter is not limited to them. In general, techniques for noisemodulation for on-chip noise measurement as described herein may beimplemented with facilities consistent with any hardware system orhardware systems. Many variations, modifications, additions, andimprovements are possible.

Plural instances may be provided for components, operations, orstructures described herein as a single instance. Finally, boundariesbetween various components, operations, and data stores are somewhatarbitrary, and particular operations are illustrated in the context ofspecific illustrative configurations. Other allocations of functionalityare envisioned and may fall within the scope of the inventive subjectmatter. In general, structures and functionality presented as separatecomponents in the exemplary configurations may be implemented as acombined structure or component. Similarly, structures and functionalitypresented as a single component may be implemented as separatecomponents. These and other variations, modifications, additions, andimprovements may fall within the scope of the inventive subject matter.

What is claimed is:
 1. A method comprising: receiving, by an off-chipnoise estimation unit external to a computer chip, a frequency-varyingsignal produced by the computer chip, the frequency-varying signalrepresentative of an on-chip noise signal determined at an on-chipdetermination point of the computer chip, wherein the off-chip noiseestimation unit comprises at least one member of the group consisting ofan integrated circuit and a processor with associated memory;determining, by the off-chip noise estimation unit, a subset of thefrequency-varying signal; executing, by the off-chip noise estimationunit, time-to-frequency domain conversion operations to convert thesubset of the frequency-varying signal to a corresponding frequencydomain signal; and determining, by the off-chip noise estimation unit, avoltage level associated with the on-chip noise signal based, at leastin part, on frequency information extracted from the frequency domainsignal and a relationship between an input voltage provided to avoltage-controlled oscillator associated with the computer chip and anoutput frequency generated by the voltage-controlled oscillator.
 2. Themethod of claim 1, wherein an instantaneous frequency of thefrequency-varying signal varies according to an instantaneous voltagelevel of the on-chip noise signal.
 3. The method of claim 1, whereinsaid determining the voltage level associated with the on-chip noisesignal comprises: determining that an amplitude of the frequency domainsignal exceeds a predefined threshold at a first frequency of thefrequency domain signal; designating the first frequency as a resonantfrequency of the frequency domain signal, wherein the frequencyinformation includes the resonant frequency; and converting the resonantfrequency to the voltage level associated with the on-chip noise signalbased, at least in part, on the relationship between the input voltageprovided to the voltage-controlled oscillator and the output frequencygenerated by the voltage-controlled oscillator.
 4. The method of claim1, further comprising: determining a variation in the voltage level withtime based, at least in part, on the frequency information and a timeinterval that corresponds to the subset of the frequency-varying signal.5. The method of claim 1, wherein said determining, by the off-chipnoise estimation unit, the subset of the frequency-varying signalcomprises executing windowing operations on the frequency-varying signalto yield the subset of the frequency-varying signal.
 6. The method ofclaim 5, wherein a first window produced by the windowing operationsoverlaps a second window produced by the windowing operations.
 7. Themethod of claim 1, further comprising: determining whether to executenoise cancellation operations at the computer chip based on at least oneof the voltage level associated with the on-chip noise signal and anapplication executing on the computer chip.
 8. A device for estimatingvoltage on a computer chip, the device comprising: an interface tocommunicably couple the device to an off-chip measurement point for thecomputer chip; and a noise estimation unit comprising at least onemember of the group consisting of an integrated circuit and a processorwith associated memory that is external to the computer chip, the noiseestimation unit configured to: receive via the interface afrequency-varying signal produced by the computer chip, thefrequency-varying signal representative of an on-chip noise signal;determine a subset of the frequency-varying signal; executetime-to-frequency domain conversion operations to convert the subset ofthe frequency-varying signal to a corresponding frequency domain signal;and determine a voltage level associated with the on-chip noise signalbased, at least in part, on frequency information extracted from thefrequency domain signal and a relationship between an input voltageprovided to a voltage-controlled oscillator associated with the computerchip and an output frequency generated by the voltage-controlledoscillator.
 9. The device of claim 8, wherein the noise estimation unitis further configured to execute windowing operations on thefrequency-varying signal to yield the subset of the frequency-varyingsignal.
 10. The device of claim 8, wherein the noise estimation unit isfurther configured to: determine that an amplitude of the frequencydomain signal exceeds a predefined threshold at a first frequency of thefrequency domain signal; identify the first frequency as a resonantfrequency of the frequency domain signal, wherein the frequencyinformation includes the resonant frequency; and convert the resonantfrequency to the voltage level associated with the on-chip noise signalbased, at least in part, on the relationship between the input voltageprovided to the voltage-controlled oscillator and the output frequencygenerated by the voltage-controlled oscillator.
 11. The device of claim8, wherein the noise estimation unit is further configured to: determinea variation in the voltage level with time based, at least in part, onthe frequency information, and a time interval that corresponds to thesubset of the frequency-varying signal.
 12. The device of claim 8,wherein the integrated circuit comprises a system on a chip.
 13. Thedevice of claim 11, wherein the integrated circuit comprises anapplication specific integrated circuit.
 14. A system comprising: acomputer chip comprising a voltage-controlled oscillator configured to:convert an on-chip noise signal determined at a determination point onthe computer chip to a frequency-varying signal; and provide thefrequency-varying signal to an off-chip measurement point for thecomputer chip; an off-chip noise estimation unit that is external to thecomputer chip, the off-chip noise estimation unit comprising at leastone member of the group consisting of an integrated circuit and aprocessor with associated memory, the off-chip noise estimation unitconfigured to: receive the frequency-varying signal via the the off-chipmeasurement point; determine a subset of the frequency-varying signal;execute time-to-frequency domain conversion operations to convert thesubset of the frequency-varying signal to a corresponding frequencydomain signal; and determine a voltage level associated with the on-chipnoise signal based, at least in part, on frequency information extractedfrom the frequency domain signal and a relationship between an inputvoltage provided to the voltage-controlled oscillator and an outputfrequency generated by the voltage-controlled oscillator.
 15. The systemof claim 14, wherein the off-chip noise estimation unit is furtherconfigured to execute windowing operations on the frequency-varyingsignal to yield the subset of the frequency-varying signal.
 16. Thesystem of claim 14, wherein the off-chip noise estimation unit isfurther configured to: determine a variation in the voltage level withtime based, at least in part, on the frequency information and a timeinterval that corresponds to the subset of the frequency-varying signal.17. The system of claim 16, wherein the off-chip noise estimation unitis further configured to: determine a reference output frequency of anoutput signal generated by the voltage-controlled oscillator for each ofa plurality of reference direct current (DC) signals provided to thevoltage-controlled oscillator; and determine a voltage-to-frequencyconversion structure based, at least in part, on the plurality ofreference DC signals and the corresponding reference output frequency,wherein the off-chip noise estimation unit is configured to determinethe voltage level associated with the on-chip noise signal using thevoltage-to-frequency conversion structure.
 18. The system of claim 16,wherein the computer chip further comprises a noise determination unitconfigured to: determine the on-chip noise signal at the determinationpoint on the computer chip; and provide the on-chip noise signal to theoff-chip measurement point.
 19. The system of claim 14, wherein theintegrated circuit comprises a system on a chip.
 20. The system of claim16, wherein the integrated circuit comprises an application specificintegrated circuit.